[serializer] introduce API to serialize internal fields

src/snapshot/deserializer.cc

Index: src/snapshot/deserializer.cc
diff --git a/src/snapshot/deserializer.cc b/src/snapshot/deserializer.cc
index 7a22a15f54f45af61e3e798ecf9777dc29fe20e5..c5cb8e5c2438345fd4a03e215540a71ee15c3af9 100644
--- a/src/snapshot/deserializer.cc
+++ b/src/snapshot/deserializer.cc
@@ -128,6 +128,7 @@ MaybeHandle<Object> Deserializer::DeserializePartial(
   Object* root;
   VisitPointer(&root);
   DeserializeDeferredObjects();
+  DeserializeInternalFields();
 
   isolate->heap()->RegisterReservationsForBlackAllocation(reservations_);
 
@@ -212,6 +213,31 @@ void Deserializer::DeserializeDeferredObjects() {
   }
 }
 
+void Deserializer::DeserializeInternalFields() {
+  if (!source_.HasMore() || source_.Get() != kInternalFieldsData) return;
+  DisallowHeapAllocation no_gc;
+  DisallowJavascriptExecution no_js(isolate_);
+  DisallowCompilation no_compile(isolate_);
+  v8::DeserializeInternalFieldsCallback callback =
+      isolate_->deserialize_internal_fields_callback();
+  DCHECK_NOT_NULL(callback);
+  for (int code = source_.Get(); code != kSynchronize; code = source_.Get()) {
+    HandleScope scope(isolate_);
+    int space = code & kSpaceMask;
+    DCHECK(space <= kNumberOfSpaces);
+    DCHECK(code - space == kNewObject);
+    Handle<JSObject> obj(JSObject::cast(GetBackReferencedObject(space)),
+                         isolate_);
+    int index = source_.GetInt();
+    int size = source_.GetInt();
+    byte* data = new byte[size];
+    source_.CopyRaw(data, size);
+    callback(v8::Utils::ToLocal(obj), index,
+             {reinterpret_cast<char*>(data), size});
+    delete[] data;
+  }
+}
+
 // Used to insert a deserialized internalized string into the string table.
 class StringTableInsertionKey : public HashTableKey {
  public: